For the first time, physicists from the University of Würzburg have successfully converted electrical signals into photons and radiated them in specific directions using a low-footprint optical antenna that is only 800 nanometres in size.
Directional antennas convert electrical signals to radio waves and emit them in a particular direction, allowing increased performance and reduced interference. This principle, which is useful in radio wave technology, could also be interesting for miniaturised light sources.
After all, almost all Internet-based communication utilises optical light communication. Directional antennas for light could be used to exchange data between different processor cores with little loss and at the speed of light.
To enable antennas to operate with the very short wavelengths of visible light, such directional antennas have to be shrunk to nanometre scale.
Würzburg physicists have now laid the foundation for this technology in a pioneering publication: In the magazine "Nature Communications", they describe for the first time how to generate directed infrared light using an electrically driven Yagi-Uda antenna made of gold.
The antenna was developed by the nano-optics working group of Professor Bert Hecht, who holds the Chair of Experimental Physics 5 at the University of Würzburg.
The name "Yagi-Uda" is derived from the two Japanese researchers, Hidetsugu Yagi and Shintaro Uda, who invented the antenna in the 1920s.
Applying the laws of optical antenna technology
What does a Yagi-Uda antenna for light look like? "Basically, it works in the same way as its big brothers for radio waves ," explains Dr. René Kullock, a member of the nano-optics team. An AC voltage is applied that causes electrons in the metal to vibrate and the antennas radiate electromagnetic waves as a result.
"In the case of a Yagi-Uda antenna, however, this does not occur evenly in all directions but through the selective superposition of the radiated waves using special elements, the so-called reflectors and directors," says Kullock.
"This results in constructive interference in one direction and destructive interference in all other directions." Accordingly, such an antenna would only be able to receive light coming from the same direction when operated as a receiver.
Applying the laws of antenna technology to nanometre scale antennas that radiate light is technically challenging. Some time ago, the Würzburg physicists were already able to demonstrate that the principle of an electrically driven light antenna works. But in order to make a relatively complex Yagi-Uda antenna, they had to come up with some new ideas.
In the end, they succeeded thanks to a sophisticated production technique: "We bombarded gold with gallium ions which enabled us to cut out the antenna shape with all reflectors and directors as well as the necessary connecting wires from high-purity gold crystals with great precision," explains Bert Hecht.
In a next step, the physicists positioned a gold nano particle in the active element so that it touches one wire of the active element while keeping a distance of only one nanometre to the other wire.
"This gap is so narrow that electrons can cross it when voltage is applied using a process known as quantum tunnelling," explains Kullock. This charge motion generates vibrations with optical frequencies in the antenna which are emitted in a specific direction thanks to the special arrangement of the reflectors and directors.
Accuracy dependent on number of directors
The Würzburg researchers are fascinated by the unusual property of their novel antenna that radiates light in a particular direction although it is very small. As in their "larger counterparts", the radio wave antennas, the directional accuracy of light emission of the new optical antenna is determined by the number of antenna elements.
"This has allowed us to build the world's smallest electrically powered light source to date which is capable of emitting light in a specific direction," Hecht details.
However, much work still needs to be done before the new invention is ready to be used in practice. Firstly, the physicists have to work on the counterpart that receives light signals. Secondly, they have to boost the efficiency and stability.
Prof. Dr. Bert Hecht, Department of Physics, University of Würzburg, Phone +49 931 31-85863, firstname.lastname@example.org
Electrically-driven Yagi-Uda antennas for light. René Kullock, Maximilian Ochs, Philipp Grimm, Monika Emmerling and Bert Hecht. Nature Communications, DOI: 10.1038/s41467-019-14011-6
Gunnar Bartsch | Julius-Maximilians-Universität Würzburg
Impact assessment of F-gas free medium voltage switchgear
30.06.2020 | Fraunhofer-Institut für Energiewirtschaft und Energiesystemtechnik IEE
Hot patterns in cold space
25.06.2020 | Fraunhofer-Institut für Werkstoff- und Strahltechnik IWS
Live event – July 1, 2020 - 11:00 to 11:45 (CET)
"Automation in Aerospace Industry @ Fraunhofer IFAM"
The Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM l Stade is presenting its forward-looking R&D portfolio for the first time at...
With an X-ray experiment at the European Synchrotron ESRF in Grenoble (France), Empa researchers were able to demonstrate how well their real-time acoustic monitoring of laser weld seams works. With almost 90 percent reliability, they detected the formation of unwanted pores that impair the quality of weld seams. Thanks to a special evaluation method based on artificial intelligence (AI), the detection process is completed in just 70 milliseconds.
Laser welding is a process suitable for joining metals and thermoplastics. It has become particularly well established in highly automated production, for...
A research team from the Max Planck Institute for the Structure of Dynamics (MPSD) and the University of Oxford has managed to drive a prototypical antiferromagnet into a new magnetic state using terahertz frequency light. Their groundbreaking method produced an effect orders of magnitude larger than previously achieved, and on ultrafast time scales. The team’s work has just been published in Nature Physics.
Magnetic materials have been a mainstay in computing technology due to their ability to permanently store information in their magnetic state. Current...
The Venus flytrap (Dionaea muscipula) takes only 100 milliseconds to trap its prey. Once their leaves, which have been transformed into snap traps, have...
NASA-NOAA's Suomi NPP satellite observed a huge Saharan dust plume streaming over the North Atlantic Ocean, beginning on June 13. Satellite data showed the dust had spread over 2,000 miles.
At NASA's Goddard Space Flight Center in Greenbelt, Maryland, Colin Seftor, an atmospheric scientist, created an animation of the dust and aerosols from the...
19.05.2020 | Event News
07.04.2020 | Event News
06.04.2020 | Event News
30.06.2020 | Physics and Astronomy
30.06.2020 | Life Sciences
30.06.2020 | Information Technology